1. Field of the Invention
The present invention relates to a method of treating starch-containing water and more particularly to a method of treating starch-containing water discharged from plants in the starch manufacturing industry; starch processing industry; food, dying and paperboard industries which utilize starch or starch derivatives; brewing industry; and rice-cake and confectionery industries, etc.
2. Description of the Background Art
Starch-Containing water discharged from plants which make use of starch will cause environmental pollution if it is directly discharged into rivers. For this reason, a reduction of starch content in discharged water down to a standard level or lower is required of these industries.
Prior methods of treating such waste water have included chemical or biological treatments.
Specific examples of the method of chemically treating starch-containing water include adding (1) an inorganic flocculant such as aluminum sulfate, (2) an organic polymer flocculant, or (3) a melamine/aldehyde acid colloidal solution consisting of alkyletherified methylol melamine and acid via a flocculation-precipitation process.
Biological waste water treating methods are also known to implement active sludge treating.
Under the chemical treating methods (1)-(2) of the prior art, soluble starch is not removable efficiently. With respect to the method (3), acid resistant equipment and apparatus is required because the additive is a strong acid. Although the soluble starch is removable, pH adjustment of the treating liquid is also required. Even if a large amount of agent is used, it still remains unfeasible to efficiently remove soluble starch using these chemical treating methods and furthermore, the compactness of the resultant precipitate becomes poor if the agent is made insoluble. Also, the throughput of the discharged water tends to decrease, the amount of the precipitated sludge tends to increase, and the loading accordingly tends to become greater.
In addition to the foregoing disadvantages, a further problem is that the active sludge treating method requires skill in operation control, a large area for facilities to be installed and a longer treating time.
The present inventors have completed the present invention as a result of studies intended for the solution of the foregoing disadvantages.